At the present time, holes are formed in high strength armor plate of the type used in tanks and other military vehicles primarily by drilling, which is time-consuming and expensive. Drills must be re-sharpened or replaced after the formation of only a relatively few holes. It is a principal object of this invention to provide a heavy duty punch capable of forming large numbers of holes in less time and hence at less cost, to provide a punch which is durable and long-lasting and to provide an improved holder for the punch.
The heavy duty punch of this invention is adapted for piercing armor plate and the like. The punch has a shank by means of which it may be held during use. The punch also has a piercing end projecting axially from the shank. The piercing end is generally cylindrical and terminates in a conical tip.
In the embodiments about to be described, the dimensions of the punch are specified for optimum performance, particularly with reference to the cone angle on the piercing end of the punch, the curve connecting the generally cylindrical surface of the piercing end with the outer margin of the conical tip, and the flare of the generally cylindrical surface of the piercing end.
Also in accordance with the specified embodiments about to be described, the holder for holding the heavy duty punch during a piercing operation comprises a body having a socket adapted to receive the shank of the punch. Gripping jaws are provided to releasably grip the shank. In one embodiment about to be described, two guide slots in the body communicate with opposite sides of the socket. The two jaws slidably mounted in the respective slots are adapted to be advanced and retracted into and out of gripping engagement with the shank. In another embodiment, one jaw is fixed and the other is slidably mounted. When the slidable jaw is advanced, the slidable and fixed jaws cooperate in gripping the shank of the punch. Means are provided for selectively advancing and retracting the gripping jaw or jaws.
Preferably, the shank of the punch is generally cylindrical but tapers outwardly relatively to the socket, and the shank-engaging surfaces of the gripping jaws taper at the same angle as the shank in order to have full surface contact therewith.
These and other objects of the invention will become apparent as the following description proceeds, especially when considered with the accompanying drawings.